TELENCEPHALOSYNAPSIS (SYNENCEPHALY) AND RHOMBENCEPHALOSYNAPSIS WITH POSTERIOR-FOSSA VENTRICULOCELE (DANDY-WALKER CYST) - AN UNUSUAL ABERRANT SYNGENETIC COMPLEX

Agenesis of the cerebellar vermis (paleocerebellar agenesis) with fusi on of the cerebellar hemispheres (rhombencephalosynapsis) is a rare ma lformation of the central nervous system (CNS). Its combination with s ynencephaly (telencephalosynapsis), telencephalic ventricular aplasia, aqueductal atresia and cystic fourth ventricle has not yet been descr ibed, as far as we know, Here, we report this combination in a 23-week s' gestation male fetus who was aboard to a 24-year-old diabetic mothe r. In this fetus with cerebral and cerebellar hemispheric fusion, verm ian agenesis was associated with a Dandy-Walker-like posterior fossa c yst, in spite of the fusion of the hypoplastic cerebellar hemispheres. The CNS malformations were further accompanied by dysmorphic facial s tigmata such as unilateral atresia of the external ear, ocular hyperte lorism and a broad nasal bridge. Preaxial polydactyly and contractures of the upper limbs were the only associated non-cranial abnormalities . Cytogenetic studies revealed a numerically and structurally normal m ale (46, XY). The malformation complex described in this fetus of a mo ther with antedating pregnancy diabetes appears to represent a previou sly undescribed aberrant syngenetic CNS phenotype, some basic teratoge netic aspects of which will be discussed in this paper. (C) 1997 Elsev ier Science B.V.